Hexagonal rod-like Eu3+doped CaMoO4 phosphors: Structural, photoluminescence and photometric properties for display device applications

Abstract

A multicolored LED illumination device is a compact, durable, easy to obtain color-adjustable output illumination source. It is frequently utilized in the domains of room illumination and exterior displays. However, the advancement of multicolor LEDs has been hampered by the rise in price and the fall in luminous efficacy while changing illumination colors. In the present investigation we have prepared intense red emitting Eu3+ doped CaMoO4 phosphor nanopowders via simple solid-state reaction technique. The powder X-ray diffraction (PXRD) studies reveal the crystalline nature of the samples with scheelite–type mono phase tetragonal structure with I41/a space group. The band gap (Eg) energy values were estimated and found to range between 4.63–5.32 eV. Scanning electron microscopy (SEM) studies reveled the hexagonal rod-like structures with different Aloe Vera gel concentrations. The particle size was found to be around 40 nm. The vibrational modes of the prepared powders were evaluated by using Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopy. It was observed from the results that, there were 26 vibrational modes of CaMoO4 (Γ=3Ag + 5Au + 5Bg + 3Bu + 5Eg + 5Eu) 8 of which (4Au and 4Eu) were infrared active and 13 (Ag, Bg, and Eg) are Raman active. Photoluminescence (PL) emission intensity increases up to 5 mol% of Eu3+ ions load and subsequently it declines due to the concentration quenching phenomenon and effective energy transfer from Mo-O charge transfer band (CTB) to 5D0 levels of Eu3+. It was noticed from PL emission spectra that, four intense peaks located at 5D0 → 7F1 (590 nm), 5D0 → 7F2 (613 nm), 5D0 → 7F3 (654 nm), 5D0 → 7F4 (702 nm) of Eu3+ respectively. The Commission International de I'Eclairage (CIE) diagram indicates the red color emission and average correlated color temperature (CCT) value was found to be 2050 K. Further, the external quantum efficiency (QE) and color purity (CP) were calculated to check the phosphor efficiency and found to be 92% and 72% respectively. The present investigation opens up a new avenue in the fabrication of low-cost display devices with high color purity and luminous efficacy.